I am pleased with the SparkFun Qwiic Speaker Amp DEV-20690 Dynamic Range Compressor but not pleased with the low frequency response. I am using the default (out of the box) settings.

The TPA2016D2 amp spec is 20 to 20kHz. I notice that Sparkfun put a 100 ohm resistor and 1.0uF capacitor in series with the inputs. (The same 100 ohm resistor and another 47nF capacitor form a 33kHz low-pass filter, which is fine.) I am worried that the series resistor and capacitor on the inputs are cutting off the low frequencies.

Using the Equation 6 on the TI data sheet, one over two Pi x Ri x Ci, I calculate a corner frequency of 1591Hz. This doesn’t make sense, so I ask this question.

What is the frequency response of Sparkfun’s Qwiic Speaker Amp DEV-20690?

The 1.0 uF input capacitor functions as a DC blocking capacitor.

The cap has impedance 1/(2PIfC), which is about 8K at 20 Hz, but to estimate the low frequency cutoff, you need to know the input impedance of the amplifier. That does not seem to be stated in the TPA2016D2 data sheet, but to extrapolate from the input current spec of 1 uA, is presumably very high, in which case 8K is negligible and not a limiting factor.

Poor perceived low frequency response is more likely to be associated with whatever transducer (speaker) you are using to reproduce the sound, and whether the amplifier has sufficient output power to drive it properly.

True. TI states the cutoff frequency is 1(2πRiCi). Your reply suggests Ri is the unstated input impedance. I took it to mean the input series resistor. Your interpretation is more accurate.

The 1uA input current at line level of 1V p-p (0 dBV) suggests an input impedance of 1 megohm, giving a low frequency cutoff of <1 Hz.

The amp drives the input of a mixer that has very good low frequency response. The speakers are driven by internal amplifiers. The mixer is likely high impedance and not meeting the “Minimum Load Resistance 3.2 ohms.” I suspect that has something to do with it.